chore(cleanup): remove unused BottomSheet component and dead testConnection

BottomSheet.svelte is not imported anywhere — NewTaskInput hand-rolls
its own sheet. SetupScreen had a standalone testConnection() function
that was only ever reachable through connectAndBrowse which calls
test_webdav_connection directly; the standalone variant had no
callers.

apps/tauri/src/lib/components/BottomSheet.svelte

@@ -1,42 +0,0 @@
-<script lang="ts">
-  import type { Snippet } from "svelte";
-  let { onclose, children }: { onclose: () => void; children: Snippet } = $props();
-</script>
-
-<!-- Backdrop -->
-<div
-  class="fixed inset-0 z-40 bg-black/40"
-  role="button"
-  tabindex="-1"
-  aria-label="Close sheet"
-  onclick={onclose}
-  onkeydown={(e) => { if (e.key === "Escape") onclose(); }}
-></div>
-
-<!-- Sheet -->
-<div
-  role="dialog"
-  aria-modal="true"
-  class="fixed bottom-0 left-0 right-0 z-50 max-h-[70vh] overflow-y-auto rounded-t-2xl bg-surface-light shadow-xl dark:bg-card-dark animate-slide-up"
->
-  <!-- Drag handle -->
-  <div class="flex justify-center py-2">
-    <div class="h-1 w-8 rounded-full bg-gray-300 dark:bg-gray-600"></div>
-  </div>
-  {@render children()}
-  <div class="h-[env(safe-area-inset-bottom)]"></div>
-</div>
-
-<style>
-  @keyframes slide-up {
-    from {
-      transform: translateY(100%);
-    }
-    to {
-      transform: translateY(0);
-    }
-  }
-  .animate-slide-up {
-    animation: slide-up 0.25s ease-out;
-  }
-</style>

apps/tauri/src/lib/screens/SetupScreen.svelte

@@ -77,20 +77,6 @@
 
   // ── WebDAV handlers ───────────────────────────────────────────────
 
-  async function testConnection() {
-    testStatus = "testing";
-    try {
-      await invoke("test_webdav_connection", {
-        url: webdavUrl,
-        username: webdavUser,
-        password: webdavPass,
-      });
-      testStatus = "ok";
-    } catch {
-      testStatus = "fail";
-    }
-  }
-
   async function connectAndBrowse() {
     testStatus = "testing";
     try {